How A Jet Engine Works
I think one of the great things about learning a language is that you can learn something else while you learn it. You have to use English to learn it, but how you use it is up to you.
It’s possible that you’ll be using technical English at your job, or when the time comes to connect your DVD player to the TV. How well can you understand technical English? I found a short video explaining–in easy-to-understand English–how a jet engine works.
when you watch it, pay attention to the vocabulary you learn. When you’re finished, would you be able to give a short–maybe twenty-second–explanation of how the engine works in your own language? Try it.
As always, if you have any questions, feel free to ask me in the comments.
UPDATE from May Third: I’ve transcribed–a fancy word for ‘written down what he says’–this video, to help you identifiy individual words. Of course, I don’t promise that I made no mistakes, so listen carefully and let me know if you find anything that needs to be corrected!
Here it goes:
The turbofan engine is a complex synchronization of several components working together as two parts. A core section that produces power to drive the propulsor section that produces thrust.
‘Thrust’ is a force that is created by the acceleration of air. This phenomenon is simply an application of Newton’s second law of motion, commonly expressed as ‘Force equals mass times acceleration.’ It is this force that propels the aircraft.
To see how this thrust is developed, let’s look at the internal working of Pratt and Whitney’s PW4102 Turbofan engine. The first component in the engine in the huge, nine foot diameter fan that rotates twenty-eight hundred times a minute at takeoff. This giant fan sucks in enough air to vacuum out the air in a four bedroom house in less than half a second. As the air races through the massive fan, it’s separated into two streams. Only fifteen percent of the air flows into the interior core of the engine. The remaining 85% of the air is ducted along the outside of the core and is forced though an ever narrowing space, the fan duct, picking up speed along the way. The ratio of this air bypassing the core to the passing through the core is called the bypass ratio.
Because of it’s huge volume, the bypassed air only needs to accelerate a small amount in order to develop an enormous amount of thrust.
Meanwhile the other fifteen percent of the air has entered the first component in the engine’s core: the low-pressure compressor. Here, the air passes through several smaller stages, each consisting of a set of rotating blades in between a set of stationary blades. Each stage compresses the air, forcing it’s temperature and pressure to rise.
After passing through the low-pressure compressor the air enters the high-pressure compressor which rotates faster and is responsible for 70% of the total pressure rise. After the air has passed through both compressors, it is 35 time higher in pressure and a thousand degrees hotter than the outside air. The compressed air is now at the right pressure, but it’s moving too fast to be efficiently ignited. So, it enters a diffuser, where it slows down while remaining at the optimum temperature and pressure.
The air then enters the combustor, where it’s energy level is greatly increased. This is accomplished by adding fuel through a series of injectors and igniting it, further increasing the temperature of the mixtures by sixteen hundred degrees. The higher the pressure of the air, the more energy will be added during combustion and the more efficient this process becomes. This is why the compressors were used to increase the air’s pressure.
Now, the super-heated and compressed air mixture is ready for the next phase: Blasting through the high pressure turbine, the high energy air spins the blades at over ten thousand revolutions per minute. These blades are connected to a shaft that runs through the center of the engine and drives the high pressure compressor. In fact, the only purpose of the high pressure turbine is to extract enough energy from the air to turn the high pressure compressor. Together, these parts make up the ‘high spool.’
Next, the air passes through the larger, low-pressure turbine. This turbine has two purposes. First, it extracts enough energy from the air to power the low-pressure compressor at the front of the engine core. These two components are connected via a second shaft, which actually passes through the center of the high spool. However, the second and more important, job of the low pressure turbine is to turn the large, titanium fan blades up front. The fan is connected to the same shaft as the low pressure compressor and low pressure turbine. Together, these three components make up the ‘low spool.’
Finally, the combusted air races through of the exhaust nozzle at the back of the engine to be accelerated one more time. The speed at which this gas leaves the nozzle is called ‘jet velocity.’ This exhaust stream produces only twenty percent of the engine’s total thrust. The remaining eighty percent is produced by the large volume of accelerated bypass air exiting the fan duct.
I hope it helps!
April 20th, 2009 at 00:34
Hey Toby. First of all thanks again helping out improvement our English. As you know I’m working at a power plant and we produse electric by using gas turbine (jet engine). . .
I watched the video several times but I can’t understand some details. Do you mind if I want you to publish or send the text of the video. It also be helpful at my work.
Thanks in advence…
April 20th, 2009 at 03:25
You are right!^^ What’s great about the English language is that it provides you with even more knowledge while you learn it. By being able to understand English, you learn all sorts of stuff especially about technical and scientific topics. In some countries, like mine for instance, science books are all in English. They are not translated into our language, so if we are not familiar with English, we would lose a lot of opportunities to learn about other very important things.
April 20th, 2009 at 05:22
Ali: First, let me answer your question. I’ll add transcribing (writing down) the text to the video to my list of things to do.
Second, a few points on your comment. Here’s how I would have written it:
First of all, thanks again for helping to improve our English. As you know, I’m working at a power plant and we produce (only a spelling error) electricity using a gas turbine (jet engine). . . [I removed the word 'by']
The rest is fine.